Wireless Networks

© National Centre for Technology in Education Nov 2008 1

The use of mobile phones has had a major impact on the way people communicate. Other
mobile devices, such as laptop computers and handheld devices have also become an
integral part of everyday life. The portability and flexibility of these devices has succeeded in
placing mobile technology in the realm of mainstream technology, both in the workplace and
the classroom.
The development of wireless networking solutions represents a significant evolutionary step in
this arena, as devices can now be fully networked even though they are not physically
connected with cables.

What is a Wireless Network?

When the term ‘wireless network’ is used today, it usually refers to a wireless local area network (WLAN). A WLAN connects computers together through radio technology using standard network rules or protocols, but without the use of cabling to connect the computers together. A WLAN can be installed as the sole network in a school or building. However, it can also be used to extend an existing wired network to areas where wiring would be too difficult or too expensive to implement, or to areas located away from the main network or building. The most obvious difference between wireless and wired networks, therefore, is that the latter uses some form of cable to connect computers together. A wireless network does not need cable to form a physical connection between computers. Wireless networks can be configured to provide the same network functionality as wired networks, ranging from simple peer-to-peer
configurations to large-scale infrastructures accommodating hundreds of users.

Wireless Network Components
There are certain parallels between the equipment used to build a WLAN and that used in a traditional wired LAN.
�� Both networks require a network interface card (NIC) that is either built-in to or added
to a handheld, laptop or desktop computer. There are two main types of plug-in card
available: PCMCIA which is inserted into the relevant slot in the side of a laptop and
PCI which is inserted into one of the internal slots in a desktop computer. Wireless
NICs contain an in-built antenna to connect with the network.
�� In a wireless network, an ‘access point’ (AP) has a similar function to the switch in
wired networks. It broadcasts and receives signals to and from the surrounding
computers via their wireless NICs. It is also the point where a wireless network can be
connected into an existing wired network.

Wireless Network Configurations
Wireless networks can be configured in ad hoc or infrastructure mode using access points.
Ad Hoc Configuration
This is the most basic wireless network configuration and is the equivalent of a wired peer-topeer network. This arrangement requires nothing more than wireless NICs in each of the connecting computers which associate through use of a common network name. However, the range of this configuration is limited and administration becomes an issue with more than just a few nodes. Thus, ad hoc configurations should only be used for the smallest of wireless networks where scalability and security are unimportant.

Infrastructure Configuration using Access Point(s)
With the installation of an access point, the range over which the network is accessible increases to approximately 150m indoors and 350m outdoors (optimum performance within 30m indoors). It is possible for an access point to support up to 30 clients, but in practice more access points are needed to support large numbers of wireless PCs . Access points are connected together via a wired LAN. The access point can also act as a bridge, allowing the wireless network to connect to a wired network.
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In a situation where users need to be mobile and still retain their connection to the network, the coverage provided by the access points should overlap. As the user moves from one area of coverage to another, the network connection is transferred from one access point to the next, without the user noticing.
Two other pieces of equipment may be required to support a wireless LAN:-
�� Extension points which act as wireless relays extend the range of an access point
�� Directional antennae may be used as a means of connecting two separate buildings
so that the network is shared between buildings.

Benefits and Educational Uses
• Installation time and costs are significantly reduced. • Network is accessible in places where wiring would have been difficult.
• The space over which a wireless network operates is not planar but spherical
providing access in rooms above or below the access point in a multi-level site
without the need for additional infrastructure.
• Teachers and students can have continuous access to the network, even as they
move with their equipment from class to class.
• Computers fitted with wireless network cards can be placed on trolleys and moved
from location to location within a school in order to facilitate group work, sharing of
files, printers and Internet access.
• Wireless range can be extended beyond the main school building to allow students
and teachers use wireless devices to gather and record data outside, e.g. as part of
a science experiment or individual performance data from a PE class.

Issues to be aware of:
Before installing wireless networks schools should be aware of the following issues:

Health Considerations
• Some health concerns have been raised that wireless networks in association with
wireless laptop computers in schools may pose a health risk to pupils, due to the
levels of radiation emitted. The Government published the Report of the Expert
Group on Health Effects of Electromagnetic Fields (EMF) on 22nd March, 2007,
which examined a wide range of issues in relation to potential health effects of EMF,
including those produced by mobile telecommunications. The Group concluded that
“so far, no adverse short or long-term health effects have been found from exposure
to the radiofrequency (RF) signals produced by mobile phones and base station
transmitters. RF signals have not been found to cause cancer.” The Department of
the Environment, Heritage and Local Government has assumed responsibility for
the health effects of EMF with effect from 1 May, 2007. The full report can be
accessed at the link below:
Wireless Speed and Reliability
• Wireless networks may seems to be a simpler alternative to networking a school
than a cabled network, however schools should not install wireless networks unless
they are aware of the potential issues and satisfied that it is the right decision for the
school. Wireless networks are significantly slower than fixed networking, by a factor
of approx 10. Wireless is also less reliable than cabled networks mainly due to
issues such as the movement of mobile PCs and possible reductions in signal
strength due to changes in the local environment. Wireless networks are typically
not suitable for schools with thick walls, including many older schools.
Security of school data:
• As wireless data travels through the air, there is a risk it could be accessed by other
parties at ranges of 100-300 metres outside of the school grounds. There is thus a
risk that sensitive school or pupil data could be accessed by unauthorised parties. In
order to prevent such an occurrence high quality wireless security software would
need to be installed by qualified companies who can provide the appropriate level of
technical support and maintenance to schools. Too often schools install wireless
networks with either no or inadequate levels of security.

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Technical and Purchasing Considerations
• If wireless is to be installed it is essential that that school receives a warranty and maintenance agreement, so that they understand the possible additional costs associated with the wireless network. The agreement should resolved issues such as reliability of signal, lack of coverage, security. A service level agreement (SLA) should be provided by the provider so that the school is aware of the extent of service provision and possible additional charges associated with the service.
• Wireless NICs are more expensive than their wired counterparts. The cost of the access points should be considered.
• Wireless networks typically work at 54Mbps which is shared between all the workstations using an access point whereas a hard-wired network connection is capable of running at 100Mbps (Fast Ethernet). A wireless network will be noticeably slower when a group of users are transferring large files. This should be considered if multimedia applications are to be delivered over the network to a significant number of
users.
• Wireless data transmission rates are dependant on the number of users, the distance from the access point and the fabric of the building (metal structures in walls may have an impact).As the range of the network may extend beyond the walls of the building, it could become accessible from outside. Consideration should be given to what security features the equipment provides to ensure that only authorised users have access to the network and that data is protected.

Relevant Web Sites

http://www.wi-fi.org/knowledge_center_overview.php
www.ncte.ie/ICTAdviceSupport/AdviceSheets

Posted in: Wireless